Maricopa County officials will subpoena records that Sheriff Joe Arpaio's office has refused to turn over to U.S. Department of Justice lawyers who are investigating the police agency over allegations of discrimination and unconstitutional searches.

A lawyer for an Arizona sheriff known for his efforts against illegal immigrants said Thursday that the U.S. Justice Department's threat to sue over records for its civil rights investigation is premature because his client is willing to cooperate with certain elements of the probe.

The Obama administration sued Arizona July 6 to throw out the state's toughest-in-the-nation immigration law and keep other states from copying it. The lawsuit, filed in federal court in Phoenix, said the law usurps the federal government's "pre-eminent authority" under the Constitution to regulate immigration.